18 February 2013

Congrats to Australia!

Australia dominated West Indies to win the Women's Cricket World Cup.  The win marks the sixth overall for the Southern Stars.  Congratulations to Australia!

There is a great deal of fascinating physics in the sport of cricket.  A lot of research has focused on cricket ball aerodynamics.  My introduction to that line of research came in the form of well-written papers by Rabindra D Mehta of the NASA Ames Research Center in Moffett Field, California.  Mehta's classic 1985 paper "Aerodynamics of Sports Balls" in Annual Review of Fluid Mechanics (vol 17, pp 151-189) describes swing bowling.  His 2005 paper "An overview of cricket ball swing" in Sports Engineering (vol 8, pp 181-192) has cogent descriptions of reverse swing, a phenomenon achieved by fast (over 90 mph = 145 km/hr) bowlers or with balls that have been strategically scuffed.  Look up those papers if you want more details than what follows.

The side-to-side movement of a cricket ball boils down to getting an asymmetric deflection of air off the back side of the ball.  The rough seams usually help delay the separation of the boundary layer of air from the ball.  If you've ever thrown a Whiffle Ball, you know that the ball deflects toward the holes, ie the rougher part of the ball's surface.  Air moving over a cricket ball that has a seam predominately on one side and a smooth side on the other will make the ball move toward the seam side.  The reverse of that effect can happen if the ball is thrown very fast, fast enough that air flow over the entire ball is turbulent.  In that situation, the seams actually serve to help separate the boundary layer closer to the front of the ball compared to the smooth side.  That leads to reverse swing.

Cricket news doesn't make for much water-cooler chat in the US.  In countries like India, Australia, and England (just to name a few), sports fans care a great deal about cricket.  Though I played cricket only a few times while in graduate school, I enjoy following the World Cup for each gender.  I especially love all the great physics to be learned in studying cricket!

12 February 2013

Enjoy Darwin Day!

Today marks the 204th anniversary of the birth of Charles Robert Darwin.  In the 74,510 days since Darwin's birth, our growing understanding of life has given us remarkable ways to view our place in the universe.  One aspect of that understanding that particularly fascinates me is our kinship with all living creatures.  What an exciting way to think about the natural world!

The scientific pursuit of truth involves the acquisition of data and evidence to support propositions.  We need not "believe" a scientific proposition.  If data and evidence don't exist to support a given proposition, that proposition won't be accepted as a description of nature.  Scientists go where the evidence takes us, and we do not fear overturning previously-held ideas.  We continually try to falsify claims; failure to do so for a particular claim leads us to the conclusion that that claim glimpses a truth in nature.  We accept what we find whether we like the results or not.  Removing confirmation bias and solipsism is not always easy, but good science requires it.  Galileo Galilei supposedly said "eppur si muove" prior to the Inquisition.  Most likely apocryphal, "and yet it moves," in reference to the Earth's motion around the sun, the remark is now used to get the point across that our beliefs are irrelevant when it comes to data and evidence acquired through scientific inquiry.

The evidence to support evolution is overwhelming.  It does not require "belief," even though people are often asked if they "believe" in evolution.  Denying evolution is tantamount to denying, for example, what we know about gravity.  A Gallup Poll published last year (click here for the story) reveals an embarrassing low percentage of US citizens who accept the scientific claims associated with evolution.  A 2006 article in Science showed public acceptance of evolution in the US to be next to last among the 34 countries surveyed (click here for the country chart).  The richest country in human history with the ability to provide public education to its citizens should be chagrined by its lack of scientific literacy, especially given that On the Origin of Species was published almost 154 years ago.

The good news is that days like today have meaning.  We celebrate the ideas that revolutionized our understanding of the natural world. With the ever-increasing advance of technology and the spread of information, we should be hopeful that scientific literacy will improve.  Darwin Day helps in this effort.  People like Congressman Rush Holt of New Jersey help, too.  A physicist, Holt led the effort to have today recognized as Darwin Day in the US.  Kudos to Dr Holt!

If you know very little about Darwin's ideas, there are many easy-to-read books out there.  I love The Greatest Show on Earth by Richard Dawkins (click here to get it).  Neil Shubin's Your Inner Fish (click here to get it) is also a wonderful read with a concluding chapter that you'll want to read twice (at least!).  Never feel ashamed if you are ignorant about something.  Knowing everything would mean never being able to experience the thrill of learning.

Have a great Darwin Day!